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RSS2018 Vol. 37, No. 3
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2018, 37(3): 329-336.
doi: 10.13433/j.cnki.1003-8728.2018.0301
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Abstract:
A complete rigid body dynamic models is established based on the virtual work principle, and the components of the dynamic models, i.e. the inertia moment term, the inertial force term and gravity term, are classified. After analyzing the slave arm movements on the contribution of the components of the manipulator torques, a simplified strategy for the rigid body dynamic models based on combinatorial mass distribution coefficients is presented; The degree of approximation between the simplified and complete models is introduced as an optimization objective, and an optimization index for minimizing the torque deviations between the two models during the motion of the manipulator is formulated in order to determine the combinatorial mass distribution coefficients; Based on the simplified method and considering the length and movement trajectory parameters of the manipulator, simulation of the parameters influence on the accuracy of the simplified models is implemented with the multi-factor analysis method, and the results show that the simplified models has higher computation speed and accuracy for different the length and movement trajectory parameters.
A complete rigid body dynamic models is established based on the virtual work principle, and the components of the dynamic models, i.e. the inertia moment term, the inertial force term and gravity term, are classified. After analyzing the slave arm movements on the contribution of the components of the manipulator torques, a simplified strategy for the rigid body dynamic models based on combinatorial mass distribution coefficients is presented; The degree of approximation between the simplified and complete models is introduced as an optimization objective, and an optimization index for minimizing the torque deviations between the two models during the motion of the manipulator is formulated in order to determine the combinatorial mass distribution coefficients; Based on the simplified method and considering the length and movement trajectory parameters of the manipulator, simulation of the parameters influence on the accuracy of the simplified models is implemented with the multi-factor analysis method, and the results show that the simplified models has higher computation speed and accuracy for different the length and movement trajectory parameters.
2018, 37(3): 337-343.
doi: 10.13433/j.cnki.1003-8728.2018.0302
Abstract:
With the development of low wind speed wind farm, the low wind speed horizontal-axis wind turbine(HAWT) is faced to the increasing large rotor and changeable wind condition. To improve the cost effectiveness of energy, weight-reduction techniques are widely used for large scaled blade. This results in lighter and more flexible rotor blades. It makes sense to develop a more accurate fluid solid interaction (FSI) model. The changeable wind condition leads to longer operation under yawed condition. In this study, a load control strategy is introduced by applying a nonlinear FSI model. The nonlinear FSI model has been developed by coupling a geometrically exact beam (GEB) with a free-vortex wake (FVW) model. The results demonstrate that this load control strategy can decrease the load fluctuation efficiently without a complex control system and additional sensors.
With the development of low wind speed wind farm, the low wind speed horizontal-axis wind turbine(HAWT) is faced to the increasing large rotor and changeable wind condition. To improve the cost effectiveness of energy, weight-reduction techniques are widely used for large scaled blade. This results in lighter and more flexible rotor blades. It makes sense to develop a more accurate fluid solid interaction (FSI) model. The changeable wind condition leads to longer operation under yawed condition. In this study, a load control strategy is introduced by applying a nonlinear FSI model. The nonlinear FSI model has been developed by coupling a geometrically exact beam (GEB) with a free-vortex wake (FVW) model. The results demonstrate that this load control strategy can decrease the load fluctuation efficiently without a complex control system and additional sensors.
2018, 37(3): 344-351.
doi: 10.13433/j.cnki.1003-8728.2018.0303
Abstract:
To study the engine cylinder head thermal state with the thermo-mechanical coupling, the temperature, the coupling stress and the cylinder head thermal fatigue were analyzed making use of fluid-structure interaction. Based on the Latin hypercube method, the elliptical basis functions neural network model was established to describe the relationship among the burning intensity, coolant flow parameters, mechanical load, the maximum coupling stress and the low-cyclic fatigue factor, and the main impact factors were studied. The results show that in the burning intensity the temperature and heat transfer coefficient of cylinder have a large impact on the maximum coupling stress and the low-cyclic fatigue factor. Improving the inlet temperature of coolant can decrease the low-cyclic fatigue factor, but increase the temperature of cylinder head. Improving the inlet flow of coolant can decrease the temperature of cylinder head, but increase the low-cyclic fatigue factor. The maximum explosive pressure has significant effect on the low-cyclic fatigue factor, and the stress pretension force has significant effect on the maximum coupling stress.
To study the engine cylinder head thermal state with the thermo-mechanical coupling, the temperature, the coupling stress and the cylinder head thermal fatigue were analyzed making use of fluid-structure interaction. Based on the Latin hypercube method, the elliptical basis functions neural network model was established to describe the relationship among the burning intensity, coolant flow parameters, mechanical load, the maximum coupling stress and the low-cyclic fatigue factor, and the main impact factors were studied. The results show that in the burning intensity the temperature and heat transfer coefficient of cylinder have a large impact on the maximum coupling stress and the low-cyclic fatigue factor. Improving the inlet temperature of coolant can decrease the low-cyclic fatigue factor, but increase the temperature of cylinder head. Improving the inlet flow of coolant can decrease the temperature of cylinder head, but increase the low-cyclic fatigue factor. The maximum explosive pressure has significant effect on the low-cyclic fatigue factor, and the stress pretension force has significant effect on the maximum coupling stress.
2018, 37(3): 352-357.
doi: 10.13433/j.cnki.1003-8728.2018.0304
Abstract:
To overcome the problem of using supervised learning to extract fault features for most current rolling bearing fault diagnosis methods, a deep neural network algorithm is proposed, which is realized sparse auto-encoder, to achieve unsupervised feature learning by automatic extracting the inherent characteristics of the rolling bearing vibration signal for fault diagnosis of rolling bearing fault diagnosis. Firstly, the spectrum of the bearing vibration signal is used to train sparse auto-encoder in order to obtain parameters; secondly, the parameters from sparse auto-encoder and spectrum of the rolling bearing vibration signal are used to train the deep neural network, and the back-propagation algorithm is used for fine-tuning the deep neural network with the purpose of improving classification accuracy. Finally, the deep neural network has been trained to identify faults of rolling bearings. The analysis results from vibration signals with roller normal condition of the rolling bearing,pitting fault of bearing outer ring, pitting fault of bearing inner ring and crack fault of bearing rolling element show that, compared with back propagation neural network, the proposed deep neural network can accurately identify fault type of rolling bearing faults.
To overcome the problem of using supervised learning to extract fault features for most current rolling bearing fault diagnosis methods, a deep neural network algorithm is proposed, which is realized sparse auto-encoder, to achieve unsupervised feature learning by automatic extracting the inherent characteristics of the rolling bearing vibration signal for fault diagnosis of rolling bearing fault diagnosis. Firstly, the spectrum of the bearing vibration signal is used to train sparse auto-encoder in order to obtain parameters; secondly, the parameters from sparse auto-encoder and spectrum of the rolling bearing vibration signal are used to train the deep neural network, and the back-propagation algorithm is used for fine-tuning the deep neural network with the purpose of improving classification accuracy. Finally, the deep neural network has been trained to identify faults of rolling bearings. The analysis results from vibration signals with roller normal condition of the rolling bearing,pitting fault of bearing outer ring, pitting fault of bearing inner ring and crack fault of bearing rolling element show that, compared with back propagation neural network, the proposed deep neural network can accurately identify fault type of rolling bearing faults.
2018, 37(3): 358-363.
doi: 10.13433/j.cnki.1003-8728.2018.0305
Abstract:
For a certain type of aircraft landing gear mechanism, considering the characteristics of random and time-varying of the load and resistance, the time-varying global reliability sensitivity analysis theory is used to study the effect and interaction mechanism of random factors on the landing gear mechanism. The output response of each input variable sample value is obtained with the joint simulation of MATLAB and ADAMS. Based on the neural network and adaptive Kriging model, the agent model of limit state function is established. Sampling method is used to realize the calculation of time-variant reliability and time-varying global reliability sensitivity of the landing gear mechanism.
For a certain type of aircraft landing gear mechanism, considering the characteristics of random and time-varying of the load and resistance, the time-varying global reliability sensitivity analysis theory is used to study the effect and interaction mechanism of random factors on the landing gear mechanism. The output response of each input variable sample value is obtained with the joint simulation of MATLAB and ADAMS. Based on the neural network and adaptive Kriging model, the agent model of limit state function is established. Sampling method is used to realize the calculation of time-variant reliability and time-varying global reliability sensitivity of the landing gear mechanism.
2018, 37(3): 364-371.
doi: 10.13433/j.cnki.1003-8728.2018.0306
Abstract:
The paper studies the influence of contact performance of spiral bevel gears with relative position errors to pre-control the meshing performance of the spiral bevel gears manufactured with the duplex helical method. According to the meshing principle of the spiral bevel gears and numerical calculation, the paper obtained the distribution of discrete mesh points. The finite element loading contact analysis of spiral bevel gear pairs is conducted in different relative positional error conditions, and the rules for changing a single tooth's normal contact force in the meshing period are gained. The results show that the mounting distance error of a pinion is more sensitive than that of other transmission devices and of normal contact force. The experimental study of the influence of spiral bevel gears on the tooth contact position and contact pressure is conducted to verify the reliability of the finite element analysis.
The paper studies the influence of contact performance of spiral bevel gears with relative position errors to pre-control the meshing performance of the spiral bevel gears manufactured with the duplex helical method. According to the meshing principle of the spiral bevel gears and numerical calculation, the paper obtained the distribution of discrete mesh points. The finite element loading contact analysis of spiral bevel gear pairs is conducted in different relative positional error conditions, and the rules for changing a single tooth's normal contact force in the meshing period are gained. The results show that the mounting distance error of a pinion is more sensitive than that of other transmission devices and of normal contact force. The experimental study of the influence of spiral bevel gears on the tooth contact position and contact pressure is conducted to verify the reliability of the finite element analysis.
2018, 37(3): 372-379.
doi: 10.13433/j.cnki.1003-8728.2018.0307
Abstract:
A novel method of elastic robot leg hybrid design was proposed. A new kind of robot leg called LCS (Linkage cable-drive spring) leg was presented, whose structure is simple but possesses excellent motion performance and strong impact resistance ability. The LCS leg was designed by adopting an elastic linkage and cable-drive system, which improves the leg's reaction rate and vibration impact resistance performance. The kinematic model of the leg was built based on the complex vector and Denavit-Hartenberg method; then the motion envelope domains were solved to verify the leg's obstacle overcoming performance. A single leg simulation platform was designed. The simulation of two kinds of robotic legs were carried out on the platform, and the CoM displacement of body, forward velocity and impact force were tested and analyzed to prove the motion performance. Through making the single leg walking experiments on the platform, the validity of the design method is verified, and the overall structural design of LCS robotic leg was carried out.
A novel method of elastic robot leg hybrid design was proposed. A new kind of robot leg called LCS (Linkage cable-drive spring) leg was presented, whose structure is simple but possesses excellent motion performance and strong impact resistance ability. The LCS leg was designed by adopting an elastic linkage and cable-drive system, which improves the leg's reaction rate and vibration impact resistance performance. The kinematic model of the leg was built based on the complex vector and Denavit-Hartenberg method; then the motion envelope domains were solved to verify the leg's obstacle overcoming performance. A single leg simulation platform was designed. The simulation of two kinds of robotic legs were carried out on the platform, and the CoM displacement of body, forward velocity and impact force were tested and analyzed to prove the motion performance. Through making the single leg walking experiments on the platform, the validity of the design method is verified, and the overall structural design of LCS robotic leg was carried out.
2018, 37(3): 380-385.
doi: 10.13433/j.cnki.1003-8728.2018.0308
Abstract:
In order to obtain six links Assur group model synthesis with multiple joints, a configuration method depend on Assur group eigenvalue with multiple is come up. Analyzing for Assur group eigenvalue, the relationship among components,multiple joints,loops and external kinematic pairs are obtained. On the basis of the above analysis, sxi links Assur group with multiple number synthesis is obtained with C language programming. Furthermore, the drawing principle and method about Assur group topology figure with multiple are given. Combining the Assur group eigenvalue with these principles about topology with multiple, a model synthesis for six group with multiple can be quickly and accurately carried out. The type synthesis about six links Assur group with multiple joints are listed. It is abundant with model synthesis about Assur group with multiple joints and laid a solid foundation to achieve the automatic drawing of the computer.
In order to obtain six links Assur group model synthesis with multiple joints, a configuration method depend on Assur group eigenvalue with multiple is come up. Analyzing for Assur group eigenvalue, the relationship among components,multiple joints,loops and external kinematic pairs are obtained. On the basis of the above analysis, sxi links Assur group with multiple number synthesis is obtained with C language programming. Furthermore, the drawing principle and method about Assur group topology figure with multiple are given. Combining the Assur group eigenvalue with these principles about topology with multiple, a model synthesis for six group with multiple can be quickly and accurately carried out. The type synthesis about six links Assur group with multiple joints are listed. It is abundant with model synthesis about Assur group with multiple joints and laid a solid foundation to achieve the automatic drawing of the computer.
2018, 37(3): 386-390.
doi: 10.13433/j.cnki.1003-8728.2018.0309
Abstract:
To effectively identify the fault features of a tractor reducer, a fault diagnosis method based on the improved inherent time-scale decomposition (ITD) and slice bispectrum is proposed. The improved ITD method adopted the segmented cubic Hermit interpolation to obtain the envelope of the signal, and is used to decompose the reducer fault signal into several inherent components, the correlation component is selected and the slice bispectrum is obtained. Based on the nonlinear characteristics of the secondary phase coupling, the frequency of fault feature is found by comparing the spectral spectrum with the slice bispectrum. The simulation results show that the improved ITD method and slice bispectrum can eliminate the information on non-quadratic phase coupling and extract fault features accurately.
To effectively identify the fault features of a tractor reducer, a fault diagnosis method based on the improved inherent time-scale decomposition (ITD) and slice bispectrum is proposed. The improved ITD method adopted the segmented cubic Hermit interpolation to obtain the envelope of the signal, and is used to decompose the reducer fault signal into several inherent components, the correlation component is selected and the slice bispectrum is obtained. Based on the nonlinear characteristics of the secondary phase coupling, the frequency of fault feature is found by comparing the spectral spectrum with the slice bispectrum. The simulation results show that the improved ITD method and slice bispectrum can eliminate the information on non-quadratic phase coupling and extract fault features accurately.
2018, 37(3): 391-395.
doi: 10.13433/j.cnki.1003-8728.2018.0310
Abstract:
According to the problems of parameter selection and feature extraction for vibration diagnosis of traditional internal combustion (I.C) engine, a new fault diagnosis method is discussed. The method based on S-transformation and Module Two Dimensional Principal Components Analysis (M-2DPCA) is proposed to carry out fault diagnosis of I.C. engine valve mechanism. First of all, the method transfers cylinder surface vibration signals of I.C. engine into images through S-transform. Second extracting the optimized projection vectors from the general distribution G which is obtained by all sample sub-images, so that vibration spectrum images can be modularized using M-2DPCA. At last, these features matrix obtained from images project will served as the enters of nearest neighbor classifier, it is used to achieve fault types' division. The method is applied to the diagnosis example of the vibration signal of the valve mechanism eight operating modes, recognition rate up to 94.17%; the effectiveness of the proposed method is proved.
According to the problems of parameter selection and feature extraction for vibration diagnosis of traditional internal combustion (I.C) engine, a new fault diagnosis method is discussed. The method based on S-transformation and Module Two Dimensional Principal Components Analysis (M-2DPCA) is proposed to carry out fault diagnosis of I.C. engine valve mechanism. First of all, the method transfers cylinder surface vibration signals of I.C. engine into images through S-transform. Second extracting the optimized projection vectors from the general distribution G which is obtained by all sample sub-images, so that vibration spectrum images can be modularized using M-2DPCA. At last, these features matrix obtained from images project will served as the enters of nearest neighbor classifier, it is used to achieve fault types' division. The method is applied to the diagnosis example of the vibration signal of the valve mechanism eight operating modes, recognition rate up to 94.17%; the effectiveness of the proposed method is proved.
2018, 37(3): 396-401.
doi: 10.13433/j.cnki.1003-8728.2018.0311
Abstract:
This paper presents the improved design of an annular water-air jet pump. The internal air-water two-phase flow characteristics of both conventional and improved annular water-air jet pumps were numerically investigated with the adopted Realizable k-ε turbulence model. In addition, the air-water interface development was visualized by steady and unsteady numerical simulations. The numerical results demonstrate a 10% increase of air entrainment compared with the conventional design, which is mostly attributable to the improved mass and energy transfer process due to the introduction of self-excited oscillation effect. This study contributes to a better understanding of the annular water-air jet pump's flow mechanism and demonstrates the feasibility of incorporating self-excited oscillation cavity into annular water-air jet pump design.
This paper presents the improved design of an annular water-air jet pump. The internal air-water two-phase flow characteristics of both conventional and improved annular water-air jet pumps were numerically investigated with the adopted Realizable k-ε turbulence model. In addition, the air-water interface development was visualized by steady and unsteady numerical simulations. The numerical results demonstrate a 10% increase of air entrainment compared with the conventional design, which is mostly attributable to the improved mass and energy transfer process due to the introduction of self-excited oscillation effect. This study contributes to a better understanding of the annular water-air jet pump's flow mechanism and demonstrates the feasibility of incorporating self-excited oscillation cavity into annular water-air jet pump design.
2018, 37(3): 402-408.
doi: 10.13433/j.cnki.1003-8728.2018.0312
Abstract:
To improve the reliability and efficiency of the computer simulation of planar multibody system dynamics, the corresponding vector bond graph method is proposed. From the algebraic relations of input and output vectors in the basic fields and junction structure of the system's vector bond graph model, the unified formulae of the system's state equations and joint's constraint force equations are easily derived automatically by a computer. From the kinematic constraint condition, the vector bond graph model of the 3-RRR planar parallel robot mechanism is established by assembling the vector bond graph model of planar moving rigid body and revolute joint. The effective decoupling method overcomes the algebraic difficulty caused by differential causality and nonlinear junction structure in the computer simulation of the system's dynamics. Based on these, the computer automatic dynamic modeling and simulation of the 3-RRR planar parallel robot mechanism are realized, and the reliability and validity of the method proposed is verified.
To improve the reliability and efficiency of the computer simulation of planar multibody system dynamics, the corresponding vector bond graph method is proposed. From the algebraic relations of input and output vectors in the basic fields and junction structure of the system's vector bond graph model, the unified formulae of the system's state equations and joint's constraint force equations are easily derived automatically by a computer. From the kinematic constraint condition, the vector bond graph model of the 3-RRR planar parallel robot mechanism is established by assembling the vector bond graph model of planar moving rigid body and revolute joint. The effective decoupling method overcomes the algebraic difficulty caused by differential causality and nonlinear junction structure in the computer simulation of the system's dynamics. Based on these, the computer automatic dynamic modeling and simulation of the 3-RRR planar parallel robot mechanism are realized, and the reliability and validity of the method proposed is verified.
2018, 37(3): 409-417.
doi: 10.13433/j.cnki.1003-8728.2018.0313
Abstract:
In order to design wear-comfortable and anti-slip earphones, the shape difference and classification of the auricular conchae were studied based on the investigation to 310 young Chinese (169 males and 141females) aged 18 to 28 years. The study combined curvature theory with RhinoScript secondary development to extract 3D coordinates of 5 characteristic points from each 3D digital model (obtained by scanning 310 ear impression prototypes) automatically, then 10 characteristic distances can be obtained accurately. The statistical analysis was carried out on the shape differences of the auricular conchae by SPSS. The results showed that the shapes of the auricular conchae among the participants existed significant differences, and the average dimensions of auricular conchae for males are generally larger than those for females. Furthermore, the auricular conchae shapes were classified into 27 groups based on the characteristic distances. For each group, the coordinates of 5 common-characteristic points were determined and the basic shape was summarized. Statistically, the percentage of the samples in each group was given and 6 prioritized groups were suggested by considering the percentage to be more than 5%. Finally, this study demonstrated the feasibility of the classification method by the design of earphone, 3D print and wear verification.
In order to design wear-comfortable and anti-slip earphones, the shape difference and classification of the auricular conchae were studied based on the investigation to 310 young Chinese (169 males and 141females) aged 18 to 28 years. The study combined curvature theory with RhinoScript secondary development to extract 3D coordinates of 5 characteristic points from each 3D digital model (obtained by scanning 310 ear impression prototypes) automatically, then 10 characteristic distances can be obtained accurately. The statistical analysis was carried out on the shape differences of the auricular conchae by SPSS. The results showed that the shapes of the auricular conchae among the participants existed significant differences, and the average dimensions of auricular conchae for males are generally larger than those for females. Furthermore, the auricular conchae shapes were classified into 27 groups based on the characteristic distances. For each group, the coordinates of 5 common-characteristic points were determined and the basic shape was summarized. Statistically, the percentage of the samples in each group was given and 6 prioritized groups were suggested by considering the percentage to be more than 5%. Finally, this study demonstrated the feasibility of the classification method by the design of earphone, 3D print and wear verification.
2018, 37(3): 418-423.
doi: 10.13433/j.cnki.1003-8728.2018.0314
Abstract:
Conformal 3D printing is a technique for manufacturing the conformal structure on the freedom surface of the bearing surface by means of 3D printing. A conformal 3D printing platform is established with the 3D direct writing technology and the manipulator control technology with six-degrees freedom. This paper analyzes the structure of the data stream generated by the conformal 3D print path on the curved surface, and discusses the generation method of the trajectory path. Tool path information on curved surface in CAM acts as a medium. The manipulator system and CAD/CAM system are connected by the code conversion program. According to the requirements of the manipulator control, the cutter path location information of tool is converted to the operation dynamic position information of manipulator by coordinate transformation and solution of rotating angle of machine tool, so that the problem of conformal 3D printing tool path generation on freedom surface is solved. The high precision printing of the conformal structure of the curved surface is completed, which proves the feasibility of this method.
Conformal 3D printing is a technique for manufacturing the conformal structure on the freedom surface of the bearing surface by means of 3D printing. A conformal 3D printing platform is established with the 3D direct writing technology and the manipulator control technology with six-degrees freedom. This paper analyzes the structure of the data stream generated by the conformal 3D print path on the curved surface, and discusses the generation method of the trajectory path. Tool path information on curved surface in CAM acts as a medium. The manipulator system and CAD/CAM system are connected by the code conversion program. According to the requirements of the manipulator control, the cutter path location information of tool is converted to the operation dynamic position information of manipulator by coordinate transformation and solution of rotating angle of machine tool, so that the problem of conformal 3D printing tool path generation on freedom surface is solved. The high precision printing of the conformal structure of the curved surface is completed, which proves the feasibility of this method.
2018, 37(3): 424-429.
doi: 10.13433/j.cnki.1003-8728.2018.0315
Abstract:
In order to study the stability of non-separated ultrasonic vibration of vertical feed direction assisted milling(NUVFAM), a dynamic model of the system is established based on the linearized theory of nonlinear periodic function and full-discretization method. Firstly, the characteristic of cutter tooth trajectory has been argued. The model of instantaneous chip thickness has been established. Then the time delay differential equations of non-separated ultrasonic vibration of vertical feed direction assisted milling have been deduced. Finally, the time delay differential equations are solved by full-discretization method. Stability prediction lobes diagrams of NUVAM systems are drawn by MATLAB7.1 software. The chatter experiments have been done under NUVFAM and normal milling on Ti6Al4V alloy. The results indicate the basic agreement of stability prediction lobes diagrams and the experimental conclusions. Under the same machining parameters, the system of NUVFAM is more stable than that of normal milling and the axial cutting depth values increase 80% at the largest.
In order to study the stability of non-separated ultrasonic vibration of vertical feed direction assisted milling(NUVFAM), a dynamic model of the system is established based on the linearized theory of nonlinear periodic function and full-discretization method. Firstly, the characteristic of cutter tooth trajectory has been argued. The model of instantaneous chip thickness has been established. Then the time delay differential equations of non-separated ultrasonic vibration of vertical feed direction assisted milling have been deduced. Finally, the time delay differential equations are solved by full-discretization method. Stability prediction lobes diagrams of NUVAM systems are drawn by MATLAB7.1 software. The chatter experiments have been done under NUVFAM and normal milling on Ti6Al4V alloy. The results indicate the basic agreement of stability prediction lobes diagrams and the experimental conclusions. Under the same machining parameters, the system of NUVFAM is more stable than that of normal milling and the axial cutting depth values increase 80% at the largest.
2018, 37(3): 430-436.
doi: 10.13433/j.cnki.1003-8728.2018.0316
Abstract:
This paper discussed the temperature field of high speed motorized spindle under various speed conditions, because the type motorized spindle belongs to built-in motor so that the heat which the motored spindle produced could not dissipate out. In order to prevent the motorized spindle from high temperature which would cause the low accuracy, the parts which produce heat and heat transfer mode are studied, then the coolant parameters which affect the temperature are analyzed. This paper fitted function related to the temperature of high-speed motorized spindle and the coolant parameter based on heat transfer theory and a large number of experimental data, and the coolant parameter model is built. Other experiment proved the model was accurate, and this paper provided important model foundation for further building the temperature control model of high speed motorized spindle.
This paper discussed the temperature field of high speed motorized spindle under various speed conditions, because the type motorized spindle belongs to built-in motor so that the heat which the motored spindle produced could not dissipate out. In order to prevent the motorized spindle from high temperature which would cause the low accuracy, the parts which produce heat and heat transfer mode are studied, then the coolant parameters which affect the temperature are analyzed. This paper fitted function related to the temperature of high-speed motorized spindle and the coolant parameter based on heat transfer theory and a large number of experimental data, and the coolant parameter model is built. Other experiment proved the model was accurate, and this paper provided important model foundation for further building the temperature control model of high speed motorized spindle.
2018, 37(3): 437-442.
doi: 10.13433/j.cnki.1003-8728.2018.0317
Abstract:
This paper aims to further improve the machining processability of wire electrical discharge machining (WEDM), and a magnetic-assisted method is proposed to improve its processing performance. Firstly, the trajectory of charged particles in discharge channel under external magnetic field is theoretically analyzed, and the movement path equation of the charged particles shows that the external magnetic field can significantly enhance charged particles to be expelled. Secondly, the magnetic pedestals of varied intensities are used as magnetic field source, and the strength of magnetic field distribution in a machining region is calculated by COMSOL simulation software. Then, the influence law of external magnetic field on the processability of different parameters is obtained with experiments. The experimental results indicate that the external magnetic field can effectively improve the processability of WEDM. Besides, there is an optimal relationship between magnetic field intensity and machining parameters. The influence law of the magnetic assisted method can provide significant reference value for practical machining process.
This paper aims to further improve the machining processability of wire electrical discharge machining (WEDM), and a magnetic-assisted method is proposed to improve its processing performance. Firstly, the trajectory of charged particles in discharge channel under external magnetic field is theoretically analyzed, and the movement path equation of the charged particles shows that the external magnetic field can significantly enhance charged particles to be expelled. Secondly, the magnetic pedestals of varied intensities are used as magnetic field source, and the strength of magnetic field distribution in a machining region is calculated by COMSOL simulation software. Then, the influence law of external magnetic field on the processability of different parameters is obtained with experiments. The experimental results indicate that the external magnetic field can effectively improve the processability of WEDM. Besides, there is an optimal relationship between magnetic field intensity and machining parameters. The influence law of the magnetic assisted method can provide significant reference value for practical machining process.
2018, 37(3): 443-450.
doi: 10.13433/j.cnki.1003-8728.2018.0318
Abstract:
Aiming at the problems of lower precision and narrower frequency band width with the semi-active vibration isolator, a kind of hybrid maglev isolator is designed, which are composed of permanent magnets and electromagnets, and the dynamic model is discussed. An improved double closed loop control strategy is proposed according to the control precision and control requirements. In the strategy, the active disturbance rejection control (ADRC) controller parameters are optimized by improved genetic algorithm, and the proportion integration differentiation (PID) controller parameters are determined via fuzzy neural network. The simulation results in MATLAB show that overshoot of the system is less than 1% after the optimal control algorithm, and the stability time of the system is shorter 1.5 s than that of the system using the traditional control strategy. Obviously, the improved control algorithm has a faster convergence speed, which makes the hybrid magnetic suspension isolator has better vibration isolation performance.
Aiming at the problems of lower precision and narrower frequency band width with the semi-active vibration isolator, a kind of hybrid maglev isolator is designed, which are composed of permanent magnets and electromagnets, and the dynamic model is discussed. An improved double closed loop control strategy is proposed according to the control precision and control requirements. In the strategy, the active disturbance rejection control (ADRC) controller parameters are optimized by improved genetic algorithm, and the proportion integration differentiation (PID) controller parameters are determined via fuzzy neural network. The simulation results in MATLAB show that overshoot of the system is less than 1% after the optimal control algorithm, and the stability time of the system is shorter 1.5 s than that of the system using the traditional control strategy. Obviously, the improved control algorithm has a faster convergence speed, which makes the hybrid magnetic suspension isolator has better vibration isolation performance.
2018, 37(3): 451-455.
doi: 10.13433/j.cnki.1003-8728.2018.0319
Abstract:
Based on the bending response curve of the lumbar spine in the sled test, a dynamic impact bending test device for dummy lumbar spine was designed and the dynamic impact test was conducted. The influence of the Shore hardness of lumbar rubber on the mechanical properties of lumbar spine was investigated. Results showed that the dynamic impact test device can reflect the dynamic impact mechanics of the lumbar spine in the sled test. The test device has the advantages of simple operation and good repeatability. Under the same dynamic impact test, there is a negative linear relationship between the hardness and the peak value of dynamic bending angle. It is indicated that when the rubber hardness increased one degree, the peak value of lumbar bending angle decreased about 0.56°.
Based on the bending response curve of the lumbar spine in the sled test, a dynamic impact bending test device for dummy lumbar spine was designed and the dynamic impact test was conducted. The influence of the Shore hardness of lumbar rubber on the mechanical properties of lumbar spine was investigated. Results showed that the dynamic impact test device can reflect the dynamic impact mechanics of the lumbar spine in the sled test. The test device has the advantages of simple operation and good repeatability. Under the same dynamic impact test, there is a negative linear relationship between the hardness and the peak value of dynamic bending angle. It is indicated that when the rubber hardness increased one degree, the peak value of lumbar bending angle decreased about 0.56°.
2018, 37(3): 456-460.
doi: 10.13433/j.cnki.1003-8728.2018.0320
Abstract:
There exists two stress state by the tensile force and shear force of lap joint weld, the differences of mechanical performance make sense for choosing weld form in engineering application. Tungsten inert gas (TIG) is used to weld 304 and 304L stainless steel. With metallographic, hardness, quasi static tensile and fatigue experiments, the structure microstructure, hardness distribution and mechanical properties of two different laps are obtained. The results show that the lap weld joint from the parent metal to the welding is divided into seven areas for the difference of microstructure. Besides, the tensile sample's elongation rate is of 19.3% and fructures at differences in the organization, while the shear sample's elongation rate is of 12.7% and fructures for size changing and stress concentration. The tensile sample has higher fracture toughness, tensile strength and fatigue damage properties, while joint strength of shear sample is significantly affected by the change in structure size and the stress concentration.
There exists two stress state by the tensile force and shear force of lap joint weld, the differences of mechanical performance make sense for choosing weld form in engineering application. Tungsten inert gas (TIG) is used to weld 304 and 304L stainless steel. With metallographic, hardness, quasi static tensile and fatigue experiments, the structure microstructure, hardness distribution and mechanical properties of two different laps are obtained. The results show that the lap weld joint from the parent metal to the welding is divided into seven areas for the difference of microstructure. Besides, the tensile sample's elongation rate is of 19.3% and fructures at differences in the organization, while the shear sample's elongation rate is of 12.7% and fructures for size changing and stress concentration. The tensile sample has higher fracture toughness, tensile strength and fatigue damage properties, while joint strength of shear sample is significantly affected by the change in structure size and the stress concentration.
2018, 37(3): 461-465.
doi: 10.13433/j.cnki.1003-8728.2018.0321
Abstract:
The austenite stainless steel is commonly considered to have a better anti-hydrogen property than martensite steel, as a result, it is extensively used in hydrogen environment of nuclear energy and chemical industry. However, the failure caused by hydrogen, mainly reversible loss of plasticity and delayed fracture, still happen. The hydrogen atoms are distributed in the near surface region of metal before the crack is formed. The surface wave travels in the near surface region of the medium. In addition, the surface wave carries most of the energy of ultrasonic wave. Thus, the surface wave can be used to discover the hydrogen damage of metal. Hydrogen atom can reduce the bonding force between metal atoms, so as to reduce the elastic modulus. As a result, hydrogen damage of metal can be discovered by evaluate the delay of surface wave travelling. The finite element analysis software ABAQUS was adopted to simulate the travelling process of surface wave in the test piece which is damaged or not. The relationship between the moment when the first crest of surface wave arrived at the middle node of the top surface of the test piece and hydrogen damage was studied. The delaying time caused by hydrogen damage is on the scale of 10-7 s, so the instrument should have high precision and resolution. The signal with higher frequency is more suitable than the one with lower frequency.
The austenite stainless steel is commonly considered to have a better anti-hydrogen property than martensite steel, as a result, it is extensively used in hydrogen environment of nuclear energy and chemical industry. However, the failure caused by hydrogen, mainly reversible loss of plasticity and delayed fracture, still happen. The hydrogen atoms are distributed in the near surface region of metal before the crack is formed. The surface wave travels in the near surface region of the medium. In addition, the surface wave carries most of the energy of ultrasonic wave. Thus, the surface wave can be used to discover the hydrogen damage of metal. Hydrogen atom can reduce the bonding force between metal atoms, so as to reduce the elastic modulus. As a result, hydrogen damage of metal can be discovered by evaluate the delay of surface wave travelling. The finite element analysis software ABAQUS was adopted to simulate the travelling process of surface wave in the test piece which is damaged or not. The relationship between the moment when the first crest of surface wave arrived at the middle node of the top surface of the test piece and hydrogen damage was studied. The delaying time caused by hydrogen damage is on the scale of 10-7 s, so the instrument should have high precision and resolution. The signal with higher frequency is more suitable than the one with lower frequency.
2018, 37(3): 466-474.
doi: 10.13433/j.cnki.1003-8728.2018.0322
Abstract:
Composite corrugated beam is widely used for excellent specific energy absorption characteristics. However the structure parameters and material properties of the composite material have large dispersion, some of them impact on the crashworthiness of composite corrugated beam. Therefore, analysis of crashworthiness reliability by considering the uncertainty parameters which has greater impact on crashworthiness has important engineering significance. In this paper, for these non-probability uncertainty problem of elastic constants of composite material, introducing the technology of multi-dimensional ellipsoidal convex model, by combined with explicit finite element technology and response surface modelling technology, uncertainty propagation analysis is conducted, so as to find out the uncertainty parameters which have a great influence on the crashworthiness of corrugated beam, and then to analyze the crashworthiness reliability of corrugated beam. The results show that the crashworthiness reliability analysis method of composite material based on the multi-dimensional ellipsoidal convex model has high precision and strong practicability.
Composite corrugated beam is widely used for excellent specific energy absorption characteristics. However the structure parameters and material properties of the composite material have large dispersion, some of them impact on the crashworthiness of composite corrugated beam. Therefore, analysis of crashworthiness reliability by considering the uncertainty parameters which has greater impact on crashworthiness has important engineering significance. In this paper, for these non-probability uncertainty problem of elastic constants of composite material, introducing the technology of multi-dimensional ellipsoidal convex model, by combined with explicit finite element technology and response surface modelling technology, uncertainty propagation analysis is conducted, so as to find out the uncertainty parameters which have a great influence on the crashworthiness of corrugated beam, and then to analyze the crashworthiness reliability of corrugated beam. The results show that the crashworthiness reliability analysis method of composite material based on the multi-dimensional ellipsoidal convex model has high precision and strong practicability.
2018, 37(3): 475-480.
doi: 10.13433/j.cnki.1003-8728.2018.0323
Abstract:
A new method for the indirect monitoring tire pressure and the early warning on tire sliding wear was proposed, which is based on the pulse number of certain distance for ABS wheel speed sensor. The simulation model of host wheel system was established in MATLAB. Some new methods, including calibration of wheel, pulse number correction of the fixed distance, mean value comparison, same or different aircraft wheel comparison, minimum pulse number set of the fixed distance, threshold calibration of the fixed distance and small sample statistics, have been successfully used to detect both sides of the aircraft tire pressure and the four main wheels sliding wear numerically. The feasility of indirect monitoring method is verified by numerical simulations.
A new method for the indirect monitoring tire pressure and the early warning on tire sliding wear was proposed, which is based on the pulse number of certain distance for ABS wheel speed sensor. The simulation model of host wheel system was established in MATLAB. Some new methods, including calibration of wheel, pulse number correction of the fixed distance, mean value comparison, same or different aircraft wheel comparison, minimum pulse number set of the fixed distance, threshold calibration of the fixed distance and small sample statistics, have been successfully used to detect both sides of the aircraft tire pressure and the four main wheels sliding wear numerically. The feasility of indirect monitoring method is verified by numerical simulations.
2018, 37(3): 481-486.
doi: 10.13433/j.cnki.1003-8728.2018.0324
Abstract:
Aiming at the problem that classical washout algorithm cannot be applied well in 3-DOF parallel motion platform, a new washout algorithm for 3-DOF parallel motion platform with two rotations and one translation (2R1T) is proposed. Firstly, the kinematic model of 3-PRS mechanism is established. Secondly, a new washout algorithm is formulated by introducing the transfer matrix from parasitic motion to Euler angular velocity. Finally, a model combined the human vestibular system and washout algorithm is established in MATLAB/Simulink to obtain simulation results. It is verified that the new washout algorithm has a fine performance and a close fidelity of cueing motion with the classical washout algorithms for 6-DOF parallel motion platform.
Aiming at the problem that classical washout algorithm cannot be applied well in 3-DOF parallel motion platform, a new washout algorithm for 3-DOF parallel motion platform with two rotations and one translation (2R1T) is proposed. Firstly, the kinematic model of 3-PRS mechanism is established. Secondly, a new washout algorithm is formulated by introducing the transfer matrix from parasitic motion to Euler angular velocity. Finally, a model combined the human vestibular system and washout algorithm is established in MATLAB/Simulink to obtain simulation results. It is verified that the new washout algorithm has a fine performance and a close fidelity of cueing motion with the classical washout algorithms for 6-DOF parallel motion platform.
2018, 37(3): 487-492.
doi: 10.13433/j.cnki.1003-8728.2018.0325
Abstract:
A decision-making method of maintenance level from the view point of performance degradation for aeroengine module is proposed to support the determination on maintenance level for the aeroengine module based on feature extraction of fuzzy relation between state parameter and module maintenance level. To solve the problem of limited existing data rules, a mathematical model of fuzzy comprehensive evaluation is established. The back propagation (BP) neural network is built to train the membership function of each parameter for different maintenance level. The entropy weight method is adopted to measure the weight of the state parameter in decision-making. Finally, the computer simulation result of the high-pressure turbine module verify that the proposed decision-making method is effective and capable of providing a efficient method for making maintenance level decision for the case with more state parameter combinations.
A decision-making method of maintenance level from the view point of performance degradation for aeroengine module is proposed to support the determination on maintenance level for the aeroengine module based on feature extraction of fuzzy relation between state parameter and module maintenance level. To solve the problem of limited existing data rules, a mathematical model of fuzzy comprehensive evaluation is established. The back propagation (BP) neural network is built to train the membership function of each parameter for different maintenance level. The entropy weight method is adopted to measure the weight of the state parameter in decision-making. Finally, the computer simulation result of the high-pressure turbine module verify that the proposed decision-making method is effective and capable of providing a efficient method for making maintenance level decision for the case with more state parameter combinations.
